You or your child should not usually need any medical tests to diagnose chickenpox. You can be pretty sure that it is chickenpox if there are the key symptoms of a mild fever followed by an itchy rash, with blisters and scabs. 

Chickenpox spots are usually distinctive enough to distinguish from other rashes, although they can be confused with other conditions that affect the skin, such as insect bites or scabies (another contagious skin condition that causes intense itching).

Watch this slideshow of common skin conditions to see what scabies, insect bites and other common skin rashes look like, so that you don't confuse them with chickenpox.

If you're still uncertain about what is causing the symptoms, your GP can carry out a simple blood test to identify the virus.  

Find phone numbers for your local GPs.

When to contact your GP

1. See your GP if you're not sure whether you or your child have chickenpox.

2. Contact your GP urgently if you have been in contact with someone who has chickenpox, or you have chickenpox symptoms and:

• you are pregnant
• you have a weakened immune system (the body’s defence system)
• your baby is less than four weeks old

Chickenpox in these instances can cause serious complications, if left untreated. It is essential to seek medical advice so that you can receive any necessary treatment.

3. Contact your GP if you have chickenpox and are breastfeeding. They can advise about whether you should continue breastfeeding your baby.

Having a blood test

Once you have contacted your GP, you may need a test to see if you're already immune from chickenpox.

If you have had chickenpox in the past, it is extremely unlikely that you will develop chickenpox for a second time. If you've never had chickenpox, or you're unsure whether you've had it, you may need an immunity test.

This is a blood test that checks whether you are producing the antibodies to the chickenpox virus.

If your blood test result shows that you have the antibodies, you'll be naturally protected from the virus. If you don't have the antibodies, you'll need to be monitored closely to see if you develop chickenpox symptoms. If you do, further treatment may be needed.

Read more about chickenpox treatment.